Alternative hydraulic drive systems – independent metering
In many machines, multiple hydraulic drives (functions 1…i) are supplied by one single pump. The actuators are very often operated independently and simultaneously. The hydraulic control system has to distribute the hydraulic power among the actuators depending on their flow and pressure requirements. Continuously increasing demands on cost effectiveness, productivity and energy efficiency of machines constantly push new developments in the fields of hydraulic systems. A reasonable and promising way to fulfil these requirements is the use of independent metering valve systems (IM). By doing so, the opening cross section of the meter-out edges can be manipulated independently from the inlet and adapted to the load situation. By influencing the pressure level, regeneration and recuperation modes become feasible. This leads to higher energy efficiency of IM systems compared to conventional valve controlled systems. In addition, with the used structure the application of simple and standardized valves is possible. This lowers the investment costs. Besides good structural properties and the further degree of freedom to control the system, there are additional potentials by transferring the functionality into the electronic control device (software implementation). Thereby, the function’s flexibility increases. Despite these potentials, there are only a few industrial applications with independent metering systems. Main reasons are the complex control algorithms, lack of modular and flexible software concepts and sufficient safety concepts.